(1) Field of the Invention
The present invention relates to an optical source for a non-self luminous display device, and more particularly to a liquid crystal display device having a backlight used as an optical source for light-emitting elements which are light-emitting diodes.
(2) Description of the Related Art
In recent years, many types of liquid crystal display devices have come into use as display devices. Liquid crystal display devices are used, for example, in TV receivers and portable instruments on account of their thinness, lightweightness and energy-saving advantages.
Since these liquid crystal display devices are not self luminous, they require some means of illumination. The illumination device generally used for liquid crystal display devices is a planar illumination device known as a  backlight. In the prior art, the light-emitting source for this backlight has conventionally been a cold cathode discharge lamp. In recent years, many types of backlight for liquid crystal display devices have come into use, including those where the light-emitting source is a light-emitting element comprising a light-emitting diode (hereafter, LED).
As a liquid crystal display device using an LED as a light source, a configuration wherein plural LED are disposed in an in-line arrangement is proposed for example in Japanese Patent Application Laid-Open Publication No. S64-88426. Also, an edge-light configuration wherein LED are disposed facing the side surface of an optical guide, is disclosed in Japanese Patent Application Laid-Open Publication No. 2002-162626.
The edge-light type backlight is suitable for a liquid crystal display device having a low power consumption. In an edge-light type backlight having such a feature, since the LED and the optical guide are disposed close to each other in mutually opposite positions, when the liquid crystal display device was subjected to vibration or shock, cracks could appear in the solder part of the LED where the LED and optical guide are in contact, so that the LED might not light up. It was therefore desired to solve this problem from the viewpoint of  maintaining the reliability of the liquid crystal display device and extending its life.
It is therefore an object of the present invention, which was conceived in view of the above problem, to provide a liquid crystal display device having an edge-type backlight and a highly reliable backlight which obviates the risk that the LED will fail to become illuminated, having a high display reliability, and having a long life.